Mustapha Najjari

Numerical Analysis of Natural Buoyancy-Induced Regimes in Isosceles Triangular Cavities

This article deals with a numerical simulation of natural-convection flows using the control-volume finite-element method in isosceles triangular cavities, submitted to a uniform heat flux from below when inclined sides are maintained isothermal, without symmetry assumptions for the flow structure. The aim of the study is to examine a pitchfork bifurcation occurrence. The study provides useful information on the thermal exchange sensitivity to two governing parameters, the Rayleigh number and the tilt angle in a basin still receiving a uniform heat flux. Results show that the heated wall is not isothermal and the flow structure is sensitive to the cover tilt angle. Three regimes with two vortices or more, symmetrical or asymmetrical, can be observed. Results can be constructive for design enhancements in energy systems such as solar water distillers and air conditioning processes.

Heat Transfer Between a Porous Layer and a Forced Flow: Influence of Layer Thickness

The heat transfer between a forced flow of a pure fluid phase and a porous medium is theoretically studied. A unified enthalpy model is used to investigate the transient temperature field in the pure fluid phase and in the porous medium. Possible transition from saturated to nonsaturated porous medium is considered. From the temperature field obtained, the time variation of the local temperature and convective heat transfer coefficient at the interface porous-pure fluid regions are studied. Numerical results provide also the parametric information concerning effects of the thickness of the porous layer on theses parameters at the transient and the steady regimes.